>>1016153
Depends on whether you want to render a single image or an animation and on how the effect(s) should be applied.
Here is a quick and very simple example I came up with as a demo (pic related):

In this case I used a single material and the window coordinates to apply the gradient. You could also use the Z component of the object coordinates too, but it would behave a bit differently. In the provided image I used shading option A for two colors. shading option B can be used to have multiple shading steps. Of course more details, like the slight color spill along the edges and the grainy texture can be added into the material too. Basically anything you can think of can be added through the shader/material.

Same, or at least similar results, can be achieved with the compositor too.

Again, you need to decide for yourself which method suits your project best and experiment a bit with different styles and effects. Good luck.